My 11 week old isn't acting herself?

my 11 week has been fussy since yesterday...hardly slept last night...she ate wonderfully last nite/early morning feedings 4-5oz every two hours...thats the schedule she set and she won't eat anymore than 4-5 oz every 2 hours at...during the day she eats 5-7 oz every 2-3 hours... but since about 8 she has eaten less than 5oz all day...she has napped for only 10minutes total all day...she her poop is yellow and water...she won't take her pacifier but she sits and chews her fingers...not suck chew...but at times i can talk to her and play and she smiles and laughs and coos/talks but just like flippin a light switch she goes from my happy smiling baby to fussing, yelling, and screaming....not really crying...any ideas